1. Field of the Invention
This invention relates to a device for analyzing fluorescent light signals in which organisms previously injected with a hematoporphyrin derivative (hereinafter abbreviated as HPD) or other fluorescent substances which have a strong affinity for tumors are irradiated with laser light at predetermined positions such as the trachea, bladder, etc. in order to produce fluorescent light, and tumors in them are diagnosed by means of the intensity of the fluorescence produced at this time.
2. Prior Art Statement
Methods and devices for cancer diagnosis and therapy utilizing the photochemical reactions between laser light and fluorescent substances such as HPD which have a strong affinity for tumors have been proposed (Japanese Patent Application Disclosures Nos. SHO 59-40830 and SHO 59-40869, U.S. Pat. No. 4,556,057).
FIG. 3 is a block drawing illustrating the basic configuration of a diagnostic device of the prior art. The device of FIG. 3 is provided with an ordinary endoscopic diagnostic system 50, a photochemical reaction diagnostic/therapeutic system 51, and a fiber bunch 52. The fiber bunch 52 consists of an image guide 53 and light guides 54, 55 and 56. One end of the fiber bunch 52 is inserted into the patient's body at a position 70 suspected to be the focus, the patient having been previously given an intravenous injection of HPD, and the other end is connected to the endoscopic diagnostic system 50 and the photochemical reaction diagnostic/therapeutic system 51.
The endoscopic diagnostic system 50 consists of a white light source 57 for illuminating the tissue surface at the position 70, the light guide 54 for conducting this light, the image guide 53 for conducting images of the tissue surface to the color camera 58, and a monitor 59 for displaying images of the tissue surface picked up by the color camera 58.
The photochemical reaction diagnostic/therapeutic system 51 is equipped with a laser light source 60, a high-sensitivity camera 62, an analytical circuit 63 and a monitor 64. The laser light source 60 outputs both exciting laser light for diagnosis (405 nm) and laser light for therapy (630 nm), which is irradiated onto the position 70 by means of the light guide 55.
The fluorescence produced by the exciting light from the laser light source 60 irradiated onto the position 70 is conducted by the light guide 56 to a spectroscope 61.
Fluorescence spectrum images SP obtained from the spectroscope 61 are picked up by the high-sensitivity camera 62 which outputs video signals SVO that are arithmetically processed in the analytical circuit 63, and the images are displayed on the monitor 64 as spectrum patterns. The spectrum images SP are set within a wavelength region of 600 to 700 nm so that it will be possible to observe the spectrum with two peaks at 630 nm and 690 nm which is a characteristic of HPD fluorescence.
Since in this type of system endoscopic diagnosis and photochemical reaction diagnosis/therapy are carried out concurrently, the white light source 57 and laser light source 60 are driven to irradiate alternately, using a timesharing system. The fluorescence spectrum system from the spectroscope 61 to the monitor 64 is operated intermittently, in synchronization with the irradiation of laser light from the laser light source 60.
Using this device, during diagnosis the operator can locate the position of a cancer while viewing at the same time the tissue images on the monitor 59 and the fluorescence spectrum patterns on the monitor 64. If a cancer is discovered, the operator can perform therapy immediately by merely switching over the light from exciting light to therapeutic light. Therapy is carried out by means of a photochemical reaction between the HPD remaining in the cancerous part and the therapeutic light. This causes necrosis selectively at the cancerous part only.
Furthermore, as for the confirmation of fluorescence during diagnosis, the spectrum patterns which are unique to the fluorescence themselves are observed directly, making it possible to determine the presence of cancer easily. This can contribute greatly to the early diagnosis and therapy of cancer.
As was described above, this device utilizes the affinity of HPD for tumors in diagnosis and therapy. For diagnosis in particular, it is configured so that it detects the fluorescence spectrum from HPD.
However, as when the tissue surface is irradiated with exciting light in the 405 nm wavelength region spontaneous fluorescence is also emitted from normal tissue, the spectrum that is actually picked up consists of HPD fluorescence on which is superimposed spontaneous fluorescence in the form of background noise. This is reported in, for example, "Laser in Surgery and Medicine," 4, 49-58 (1984).
FIG. 4 shows an example of the total fluorescence spectrum intensity I.sub.TOT, the spontaneous fluorescence spectrum intensity I.sub.AUTO, and HPD fluorescence spectrum intensity I.sub.HPD. As can be seen from FIG. 4, total fluorescence spectrum intensity I.sub.TOT has HPD fluorescence spectrum intensity I.sub.HPD and spontaneous fluorescence spectrum intensity I.sub.AUTO superimposed thereon. For purposes of diagnosis this is not a problem if the spontaneous fluorescence spectrum intensity I.sub.AUTO is sufficiently smaller than HPD fluorescence spectrum intensity I.sub.HPD. In most cases, however, spontaneous fluorescence spectrum intensity I.sub.AUTO is usually about the same as HPD fluorescence spectrum intensity I.sub.HPD or greater. Also, spontaneous fluorescence spectrum intensity I.sub.AUTO and HPD fluorescence spectrum intensity I.sub.HPD are subjected to complex and extensive changes by the areal ratio of normal tissue parts to abnormal tissue parts (cancer parts) in the field of observation, the relative distance between light guides 55 and 56 and the tissue surface, and the laser irradiation angle and detection angle relative to the tissue surface. Because of this, in actual diagnosis, it has been very difficult to accurately detect the HPD fluorescence spectrum intensity I.sub.HPD.